Review & Upgrade of the Audionote kit 1

Note from editor : this article is based on my experiences and is my opinion and expresses my vision.

The kit one, a British product from Audionote UK, Mr Peter Qvortrup

Introduction to Audionote prior to the split

Audionote UK where distributors of the famous Audionote Japanese high end products they also wanted to commercialise their own products and wanted a piece of the diy kit market.

Audionote UK also made their own products and sold them under the brand name Audionote. This is their kit one, it uses 300B’s and is single end, as to Audionote they have many different tube transformers and are classified into 4 main categories, according to power, core metal specs and quality of windings and core material.

Even the power transformers and chokes can be custom ordered depending on quantity.

They are renowned for their quality so the choice of capacitors is off course dependent on the situation, hence black gates, paper in oil types and electrolytics, and silver wired ones as well.( hand made by Mr Kondo himself)

Same story on the resistive side, Holco, H2, Shinkoh tantalum ect.

With other words plenty of good materials to make some fine tube equipment .

This kit one cost originally 1490 euros.

Many other kits where also available and still are.

Presentation

The seriousness of a constructor can be judged by the care of the packing of its products, with the kit one all elements are nicely stacked and protected in frames in one big carton .

The construction notice is well written, but only available in English it seems.

Schematic

Originally 3 tubes are used per channel, the first tube only half a tube is used ,in a common cathode gain stage .the originality of this circuit lies in the volume pot being in the middle before the 2^nd tube stage, and not in the beginning.

The first tube is a 6SN7, this is a rugged tube very un micro phonic, low gain, and of universally renown quality.

This stage is biased at a 6mA.

The supplied resistors for this kit are all German, Beyschlag (no exotic types here)

The decoupling capacitor is std electrolytic!!!

The signal coupling capacitor is alu paper in oil.

The following stage uses a controversial tube, the 5687, in a SRPP configuration or totem pole. Therefore it works as a push pull pair and has some advantages excellent bandwith, low output impedance and some disadvantages (I don’t like SRPP ).

Again the decoupling capacitor is std electrolytic !!!!!!!!

The signal coupling capacitor is Jensen alu paper in oil .

The 300B stage is simple, SE output transformer and automatic bias for the output stage, with again std electrolytic capacitor.

The tube is a Chinese version, and no reason to be sad, this is one of the best and cheapest. With 2K5 and a current of 70ma and 415volt plate voltage, 8 watts of output power is claimed and obtained.

No overall feedback, and tube full wave rectification are the other characteristics of this easy to build amplifier.

The 300B filaments are dc fed and regulated, the indirect heated triodes are all heated with AC, but hum is not a problem.

Mechanical construction:

The chassis is correctly finished and has good rigidity, all holes are nicely made and doesn’t need sanding but the chassis is MAGNETIQUE.

Mount all as the manual mentions. All components are logically mounted, the output transformers are a good distance from the power transformer.

To make things easy 3 high quality printed circuits boards are used.

Conclusion

Build quality is very good, it’s a fair kit considering its pedigree but its not cheap.

Component quality is dubious, as the listening test showed, no real satisfaction available and below par sound reproduction, was it just this one model or are they all lacking in the musical reproduction department.

How did I start this thing ?

The usual thing happened I made a mod on demand of a customer who owned this amp.

In this case this amp was brought in by a customer who bought it 2^nd hand and thought that something was broken, because the sound was really not good.

But he still did buy it such is the power of a brand name and it was like this when he bought it, but the name Audio note exited him and he really wanted to own one .

So first thing I do, I check voltages without tubes, nothing wrong there!

Then I put in the tubes and listen to it, and indeed it didn’t sound very good, but nothing wrong technically to my ears: no burnt resistors or defective tubes.

So the bottom was unscrewed and I saw the 3 pcbs, 1 for the power supply, 1 for the heaters and the last one for the pre amp and drivers.

Some high quality parts were used like paper in oil coupling caps and some very cheap parts as well, worst of all is the volume potentiometer, then the cathode bypass where all just plain non decoupled electrolytic’s, in total 3 per channel.

This meant that the audio signal had 7 capacitors in its signal path, there goes simple design!

Power supply was also lousy, main effort was just to reduce hum at minimum cost.

I phoned the owner, proposed him to upgrade parts and modify the design as well because the circuit was also lousy, to much gain stages, and the 5678 tube is not really suited for hifi. (I know dozens of the BEST equipments on earth use them: not my fault it is a tube made by the thousands for early computer switching purposes)

So basically I was not sure why it sounded so bad, was it the SRPP, the 7 capacitors in the signal path or the 5687 tube or the lousy pot for volume, however because I was in doubt I decided to throw it all out!!!!

Modified schematic , ( this is a new amp actually )

See pictures of mod

.

After the mod , was it worth it ?

The Customer who turned out to be a semi professional loudspeaker builder came with his friend to pick the amp up, he really didn’t expect it to be better, not only was it so much better, it was jaw dropping and this with the std transformers, not even Lundahls and with std Chinese 300B (original Audio Note)

Even his friend told him that the amp was flawless and beyond belief improved.

All parts can be bought anywhere in any serious diy shop.

I don’t think anything is critical.

Should you attempt the mod?

Definitely yes, we are not talking about subtle differences.

Lately I also learned that Audionote UK had split with Audionote Japan.

Many of you knew that Audionote had split (I didn’t), because of a dispute between the UK distributor and the Japanese main house created by Hiroyasu Kondo.

From what I heard it’s a sad story and more could be found on the Japanese website of Kondo-Audionote. Know the name changed in Japan because the dispute also involved the possession of the brand name.

From the Japanese side the reasons I heard where that many customer complaint about the low quality of the products and Japan had nothing to do with them as they where British designed, but designed to make money mainly. (as are all businesses)

And they didn’t want to hear about problems regarding lower quality products.

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